Mobile devices have limited electrical resources. The energy output of the power sources used to furnish a regulated DC voltage, from a direct current provided by embedded batteries, is a determining factor in the length of time the device remains charged. It is desirable to increase this length of time. To allow a headset connected to a mobile device to reproduce sounds from audio data, an electrical signal amplified by an audio amplifier must be produced. The audio amplifier must therefore be supplied with sufficient power to produce at least one regulated and substantially constant voltage, ideally a positive voltage and a negative voltage that are symmetrical, typically 1.8V and −1.8V or even 0.8V and −0.8V.
One known approach for powering an audio amplifier consists of using a switched-mode power supply to provide a positive voltage to the audio amplifier and to a charge pump. From the positive voltage, the charge pump generates a negative voltage delivered to the audio amplifier. This type of setup only enables an efficiency of about 75%. The energy losses observed in the charge pump are the primary cause: in the case of a symmetrical positive voltage and negative voltage of 1.8V and −1.8V respectively, measurements show that about 400 mV are lost in the charge pump. The charge pump must therefore be supplied with a voltage of 2.2 V, which results for example in significant dissipation of energy in a linear audio amplifier for which the efficiency is about 30%. Also, in a conventional terminal comprising a battery of a capacity of between 700 and 1000 mA/H, such a setup results in a playing time of only 30 to 70 hours, depending on the nature of the audio data. In addition, such a setup typically requires the use of five condensers, an inductor, and connections occupying a silicon surface area of 0.42 mm2, in the case of a circuit etched using 130 nm technology.